Many techniques are currently used for relining underground conduits. One method of relining conduits involves the digging of a “launch trench” into which lengths of new pipe are lowered. The pipe lengths are then slid into the host pipe and are joined together to form a continuous new pipe. Generally with this method, the conduit being relined must be dry. This is often achieved by “over pumping” (pumping the water, sewerage or other fluid above the surface so that it bypasses sections of the conduit being relined).
Methods that require “over pumping” are undesirable due to the cost and complexities involved with the over pumping process.
Another method of relining underground conduits involves placing a pipe winding machine into an access pit and then feeding an elongate plastic strip into the pit. The machine then winds the strip into an elongate helical pipe. The applicant has developed various machines and methods for winding such a helical pipe. Some of these methods do not require “over pumping” and can be carried out while a conduit being relined is in service. However, these methods are not suitable for producing a welded pipe.
In some applications, it is desirable to provide a fully welded pipe. Fully welded, or continuously welded pipes, are watertight.
It is an object of the present invention to provide a method suitable for relining an operational underground pipe that eliminates or at least minimises the need for trenching and provides a continuously welded pipe.